Beryllium-antimony composition

ABSTRACT

THERE IS PROVIDED A COMPOSITION OF BERYLLIUM AND ANTIMONY CONTAINING FROM 0.1% TO 16% BY WEIGHT OF ANTIMONY AND CHARACTERIZED BY IMPROVED MACHINING CHARACTERISTICS OVER THOSE OBTAINED WITH BERYLLIUM. THERE IS ALSO PROVIDED A NEW COMPOUND OF ANTIMONY AND BERYLLIUM, SB2BE2.

United States Patent ()ffice 3,574,608 Patented Apr. 13, 1971 3,574,608 BERYLLIUM-AN'IIMONY COMPOSITION Albert James Stonehouse, Lyndhurst, Ohio, assignor to The Brush Beryllium Company, Cleveland, Ohio No Drawing. Filed Nov. 1, 1968, Ser. No. 772,864 Int. Cl. C22c 25/00, 31/00 US. Cl. 75-149 Claims ABSTRACT OF THE DISCLOSURE This invention relates, as indicated, to a composition of beryllium and antimony.

Beryllium metal in its pure and its commercial forms is a metal extremely difficult to machine without substantial damage in the form of cracks and fracturing. It is in drilling or milling of beryllium metal that these tendencies are particularly manifest. After-treatment of machined beryllium parts, e.g. etching, is usuallyrequired in order to preserve the desired mechanical properties of the metal.

It has now been found that the machining characteristics of beryllium can be improved by the inclusion of a minor amount of antimony without substantial compromise of the mechanical properties of the beryllium metal. For example, improved depth of cut and speed of out without fracture of the metal or excessive tool wear are observed. The surface finish is also improved. It has also been noted that the notch toughness of the composition is materially improved over beryllium per se. Inclusion of antimony also alleviates machining damage normally encountered in beryllium and makes it unnecessary to carry out etching operations after machining to preserve the desirable mechanical properties of the metal.

Briefly stated, then, this invention is in the provision of a beryllium base antimony composition comprising a major amount of beryllium and from 0.1% to 16% by weight of antimony.

As used herein, the term alloy means a composition of two or more metals which may consist of (a) one or more metals in solid solution in the base metal, (b) a simple mixture of one or more metals with the base metal, or (c) one or more intermetallic compounds dispersed through the base metal, or (d) combinations of (a) with (b) or (c), or both; and combinations of b) with (c). An intermetallic compound is a singlephase composition of two or more metals having a different crystal structure from any of the parent metals.

The compositions are most conveniently prepared by blending the desired amount of antimony as 325 mesh powder with '200 mesh or finer beryllium powder and following normal hot pressing procedure for beryllium powder, e.g., 1075C. and 500 p.s.i., using graphite tooling.

As conditions of hot pressing there may be utilized pressures in the range of from 70 to 2,000 p.s.i., preferably above 500 p.s.i., and temperatures in the range of from 900 to 1250 C., and preferably 1000 C. to 1150 C. In the laboratory 3 to 4 hours under these conditions is sutficient. Industrial quantities of the order of a ton or more require up to 15 hours. Reference may be had to the techniques described in the patents to Dodds 2,725,288 and 2,818,339 for manipulative procedures useful in preparing the compositions of the present invention. Blending of the powders is conveniently carried out in a ball mill, preferably with a reduced charge or shorter milling time to minimize grinding action, for a sufiicient period of time to blend the materials; for example, 2 to 6 hours.

Attempts to vacuum cast the composition result in severe loss of antimony due to volatilization and severe segregation of the antimony content in the resulting casting. If measures are taken to control these factors, vacuum casting is an alternative preparation procedure. Cold pressing and sintering of the antimony and beryllium powders may also be successfully used to form the compositions.

The metals from which the alloys or compositions of the present invention are formed are commercial grades and thus contain the normal amounts of impurities associated with these metals as obtained from commercial sources.

Typical commercial beryllium has an analysis within the following:

Percent Be 94.5 to 99.9' 0 0.1 to 4.5 Al 0.0015 to 0.1600 Fe 0.0025 to 0.2500 Si 0.0025 to 0.0800 C 0.0025 to 0.2500

Although purer metals are desirable, commercially available beryllium containing 98.5% to 99% beryllium and oxygen as beryllium oxide, the latter being present in the amount of from 1.5% to 1% by Weight, is especially satisfactory for use herein. With respect to the antimony, again although the purer metal is desirable, nevertheless antimony metal containing the normal impurities associated therewith is contemplated hereby. Antimony having a purity of 99.5% is commercially available.

Antimony has been found to be present in these compositions primarily as the binary intermetallic compound, antimony beryllide, having a composition believed to be Sb Be and having a cubic crystalline structure. This cubic phase readily undergoes ordering which creates a distorted cubic structure, possibly a tetragonal structure with the a axis only slightly different from the b axis. Quenching of the compositions from temperatures of 1200 F. or higher results in the presence of free antimony.

Sb Be appears to be the only compound in the Sb-Be binary system. Its composition as Sb Be is arrived at through density consideration based on the observed structure and X-ray diffraction patterns. The disordered (random) structure is face-centered cubic with a lattice parameter of 11.82 A. The structure most commonly observed, however, is an ordered one, the X-ray diffraction pattern containing numerous superlattice lines along with those reflections of the cubic lattice. The observed reflections are listed below in Table I. Metallographic observation substantiate the single antimonyberyllide phase having a basic cubic lattice, and also indicate an order-disorder transition in that many preparations are very faintly birefringent under polarized light.

TABLE I.X-RAY DIFFRACTION PATTERN OF She-Bea PHASE [Cu K. to 80 20] Intensity d (A.) (percent) (hkl) .16 4.10 5 3.71 8 i 3.43 100 222 3.34 3.24- 8 3.10 2.81 s 2.72 3 2.66 5 2.57 s 2.46 12 2.34- 3 2.25 10 2.103. 55 440 2.036. 2 1.782 622 1.692 3 1.653 3 1.571 2 1 .558 2 1.546- 2 1.546. 2 1.52 3 1.503 4 1.482 3 1.470 (difluse) 10 800 1.431 3 1 .410 1 1.370. 1 1,348- 10 662 1.332 3 1.31 1 1.30 1 1.28 2 1.207 10 844 1 Denotes superlattice lines which vary in intensity depending upon the degree of ordering. Intensities shown here are about the maximum which have been observed relative to the FCC lines.

The calculated X-ray density of the compound Sb Be based upon 80 atoms per unit cell (Mn O -type T structure) is 6.7 grams per cubic centimeter. This compares with a density of 5.90 grams per cubic centimeter calculated by the rule of mixtures for antimony and beryllium in the stoichiometric proportion of Sb Be A more dense configuration in the compound as compared With the parent metals is understandable in the present case.

This compound is formed by blending powdered beryllium and powdered antimony. Although Sb Be will be formed at elevated temperatures in a mixture of any proportions of the two materials, best results are secured with the beryllium being at least in excess of the amount required to form Sb Be The compound begins to form slowly at a temperature of about 550 C., the rate of formation increasing rapidly as the temperature increases to about 615 C. In this temperature range, 2 to 5 hours time is usually sufiicient. Temperatures in excess of 615 C. may be employed but difiiculty may be experienced at higher temperatures in avoiding loss of antimony unless pressure is applied. In any event, it has been found that at a temperature of from 620 C. to 630 C., the compound melts and disassociates into molten antimony and beryllium. In alloys where there is a large excess of beryllium, the compound forms rapidly upon cooling, making it difficult to maintain the high temperature equilibrium state through quenching. The same is true of the ordered state, most samples possessing some degree of ordering even though quenched from elevated temperatures. It is believed that this occurs because the orderdisorder transformation temperature is very close to the 4 melting point, or disassociation temperature, of the compound.

The hardness of the compound, measured with a gram load, varies from 375 to 426 Knoop for the random and the ordered structures, respectively.

It is contemplated in accordance with this invention, therefore, that the improved beryllium base antimony alloys may be prepared by intimately blending with beryllium metal the additive Sb Be or concentrated master alloy or concentrated mixture of Sb Be in beryllium, such that the concentration of antimony in the final beryllium-antimony composition is Within the range of from 0.1% to 16% by weight of antimony. It appears that the binary intermetallic compound, antimony beryllide, Sb Be is a new composition of matter per se that has a melting point in the range of 620630 C. This compound is easily obtained and is most useful in alloy combination with beryllium, the latter being a residual impurity in the formation of the antimony beryllide and present in an amount ranging from about 5% to about 25% by weight. This latter composition, i.e. antimony beryllide containing or mixed with excess beryllium, provides a suitable although currently more expensive additive for addition to beryllium metal to form a berylliumantimony composition of improved machining characteristics in accordance herewith.

When antimony metal is added to beryllium by the more economical procedure to provide a concentration in the range of from 0.1% to 16% by weight; antimony beryllide, 'Sb Be forms in situ, and retains its identity in the final product as formed under the usual conditions of hot pressing.

The tensile properties of hot-pressed beryllium base compositions are illustrated in Table II for compositions consisting of additions from 0% to 16% Sb by weight at room temperature. Tensile properties of 4% to 8% Sb by Weight materials at elevated temperatures are summarized in Table III. The data listed for beryllium without antimony addition were taken on hot-pressed material prepared from the same powder lot as was used in preparing the composite materials. As is standard practice, it was necessary to etch 0.002 in./side from the beryllium bars after machining operations in order to attain the properties shown. The antimony-containing materials were tested in the as-machined condition.

TABLE II.-ROOM TEMPERATURE TENSILE PROPERTIES AS A FUNCTION OF ANTIMONY CONTENT (HOT PRESSED MATERIAL) Ulti- Antimony Pressed mate Yield Percent Percent amount, density Orien- (1,000 (1,000 elongared. in percent (g./cc.) tation p.s.i.) p.s.i.) tion area 1 0.002 1n./side removed by HF-HNOa etch as is standard practice with beryllium. All other samples tested in its-machined condition.

In the foregoing table, each sample is tested in two directions as is conventional in hot-pressed beryllium technology because of the orientation which occurs in the course of hot-pressing. T stands for determinations made on the sample in a direction transverse to the direction of pressing. L signifies a test direction longitudinal to the direction of pressing the sample. These abbreviations are used also in the succeeding tables.

TABLE V.TENSILE PROPERTIES OF 6 ANTIMONY- BERYLLIUM-ANTIMONY COMPOSITION AT ELEVATED BERYLLIUM COMPOSITION IN ROLLED Sl I EET FORM AS TEMPERATURES A FUNCTION OF HEAT TREATMENT Anti- Ulti- Ultimony mate Yield Percent Percent mate Yield Percent Percent amount, Orien- (1,000 (1,000 elongared. in (1,000 (1,000 Elongared. in percent tatlon p.s.i.) p.s.i.) tion area Heat treatment p.s.i.) p.s.i.) tion area Ln rnmomh nvl o nmpmnmn omi m-b 11111111111111 L3 7 0 9 1 aLL&7 &

Gu ls-0994424960600 fi hiiemamawaiLlll LZ 5777777777777-d76 TLTLTLTLTLTLTLTLTLTLTLTLTLTLTL TABLE IIL-TENSILE PROPERTIES OF HOT PRESSED Temp,

0.125 inch milled cut, normal tooling 0.050 inch cut,

0.050 inch milled milled Cut-ofi cut,

wheel special normal surface tooling tooling red. in area depth, and a normal 1" carbide cutter with PAW/min. 30 feed (surface speed 200 ft./min.). Cuts were made with a feed of l A"/min. (surface speed 200 ft./min.) with 0.050" depth of cut using special tooling to give immaterial even with microscopic examination up to SOOX. The surface finishes resulting were:

NoTE.-Root mean square in micro-inches.

Percent The hardness of the bery11ium antimony compositions beryllium compositions using special tooling at 0.05" hereof was found to increase gradually with increasing antimon content as follows:

y Rockwell B average of depths of 0.050 and 0.125 inch. Cuts were also made at 6 determinations proved surface finishes. Under these conditions uslng nor- 9 mal tooling, the control pieces actually fractured. No evidence of fracture or cracks could be found in the alloy The beryllium-antimony compositions hereof have been found to hot roll in the same manner as does unalloyed o s n The tensile properties of 4% and 8% Sb additions to beryllium as hot rolled sheet according to conventional TABLE IV.TENS1LE PROPERTIES OF BERYLLIUM-ANTIMONY COMPO- SITIONS IN ROLLED SHEET FORM Ulti- Sb mate Yield Percent- Content, Orien- (1,000 (1,000 elongapercent tation p.s.i.) p.s.i.) tion 0 5 d m n h m a tw l mmms wwzm a .ma ma r 3.1 d 6 mn .wwm .w nm i mmmm a a V. b. Mm m S on sub H wnflml .1 bwr nwmpfi dmW n w eum a h at S 3 W w n n.w ieimw mm Haws me a Stew 1% antimony calc. as metal 83.2 2% antimony calc. as metal 4% antimony calc. as metal 84.0 8% antimony calc. as metal 84.7 1 6% antimony calc. as metal 85.7

beryllium in the region of 1400-1450 F. using conventional beryllium hot rolling techniques. Edge-cracking is notably absent from such sheets although it is quite common in the rolling of unalloyed beryllium.

hot rolling pratice for beryllium sheets and after a 12:1 reduction in rolling are shown in Table IV. In this in- Control As rolled.-

1,40o F., 4 hr. heat treat after It would appear from these data that additions of antimony in even trace quantities have beneficial effect on the machinability of beryllium.

Drilling of the beryllium-antimony composition material appears to be quite favorable with little or no break-out even when not using a back-up plate as is necessary with beryllium metal.

The beryllium base antimony compositions hereof exhibit greatly enhanced resistance to cracking and cleav- The response of the beryllium-antimony composition to heat treatment in the hot-rolled form was studied more extensively using a beryllium-6% antimony composition.

age type fracture as compared to beryllium metal. This is illustrated by the data shown in Table VI, the results of fracture toughness testing of hot-rolled sheet. The behavior of unalloyed beryllium is typified by the data given for antimony addition. The addition of anti mony raises the net fracture stress of such notched specimens to a great degree as well as markedly increasing the fracture toughness coefficient, K Fractures of the alloy materials hereof are characterized by evidence of fracture stoppage and directional changes (and shear) during fracture propagation, while unalloyed beryllium eX- hibits cleavage fracture, i.e., the fracture surface is smooth and propagation of fracture proceeds without interruption or tearing.

The corrosion behavior of the beryllium-antimony compositions has been surveyed. The standard humidity cabinet test (170 F., 98+2% relative humidity -1 cycle=2 hours to temperature, 6 hours at temperature, and 16 hours return to starting conditions with condensation) was carried out for cycles on 4%, 8%, and 16% Sb hot pressed samples. Several superficial corrosion sites were observed, but no significant weight gains. The material performed as well as the better beryllium materials and better than most. The compositions of this invention will accept both anodizing and chromate conversion coating.

TABLE VI.-I-RACTURE TOUGHNESS TESTS Norm-Specimens 1 inch wide by 3 inches 1ong, 0.0420.067 inch thick. Notch 0312-0336 inch deep, 0.002 inch machined root; K10: fracture toughness eoelficient for plane strain fracture; net fracture stress: fracture load in pounds/specimen width-notch depth divided by specimen thickness in inches.

There has thus been provided a beryllium base antimony composition which is characterized by improved machining characteristics obtained without substantial sacrifice of the normal properties of unalloyed beryllium as a structural material. The compositions hereof are conveniently made by either of two procedures. The first contemplates adding antimony metal to beryllium metal, preferably as finely divided powders, intimately blending the powders, and then submitting the blend to elevated temperatures below the melting point of beryllium but above about 900 C., and to a pressure in the range of from 70 to 2000 p.s.i., and preferably above about 500 p.s.i. Normally graphite tools are employed in this operation. Alternatively, powdered antimony beryllide, Sb Be may be added to powdered beryllium metal in the same manner and in an amount sufiicient to provide an antimony concentration of from .l% to 1 6% by Weight of the entire composition and hot pressed as above described. It is convenient to incorporate the mechanical property modifying agent, antimony beryllide, into beryllium as a concentrated master alloy or composition so that the concentration of antimony, calculated as the metal in the final product, is in the range of from .1% to 16% by weight.

What is claimed is:

1. A beryllium-antimony composition comprising a major amount of beryllium and from .1% to 16% by weight of antimony.

2. A beryllium-antimony composition in accordance with claim 1 in which the beryllium is commercially available beryllium metal containing normal impurities in the normal amounts, and the antimony is commercially available antimony metal containing the normal impurities in the normal amounts.

3. A beryllium-antimony composition comprising a major amount of beryllium and from 4% to 8% by weight of antimony.

4. A beryllium-antimony composition in accordance with claim 3 in which the beryllium is commercially available beryllium metal containing normal impurities in the normal amounts, and the antimony is commercially available antimony metal containing the normal impurities in the normal amounts.

5. A beryllium-antimony composition comprising beryllium and antimony beryllide in an amount sufficient to provide from .l% to 16% by weight of antimony calculated as the metal.

6. A beryllium composition of improved machining characteristics containing in intimate mixture therewith an amount of antimony beryllide to provide a concentration of antimony in the beryllium of from .l% to 16% by weight calculated as the metal, the remainder being substantially entirely beryllium.

7. Antimony beryllide, Sb Be dispersed in beryllium.

8. Antimony beryllide, Sb Be 9. The method of forming Sb Be which comprises blending finely divided antimony with finely divided beryllium and heating the blend to a temperature of from 550 C. to about 1250 C.

10. The method of claim 9 in which the amount of beryllium is stoichiometrically in excess of the amount required to convert the antimony present in the blend to sbgBez.

References Cited Ugai et al.: Zh. Neorgan, Khim., vol. 9, pp. 218-20,

January 1964.

L. DEWAYNE RUTLEDGE, Primary Examiner E. L. WEISE, Assistant Examiner US. Cl. X.R. -l50 32 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,574,608 Dated April 15. 1971 nv Albert James Stonehouse It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, Table I, third line of heading, "80 should read 80 Column 3, Table I, the 2 lth line is a repeat of the 23rd line and should be deleted.

Column 3, Table I, line 32, "1,5 48" should read 1 .348

Column 5, Table I, line 37, "1 .207" should read 1 .206

Column 5, Line 48, "pratice" should read practice Signed and scaled this filth day of August. 1 971 (SEAL) [attest EZJI'IAI'ZL II.;"L;IT'JETQ;;IZ,JP. wILLIM-L E5. SCIFUYLEEI, JR. Atken-iing; Of? 3 lommiezionfir of Patents 

